THE BREATH OF LIFE, Part II
CELLULAR RESPIRATION
The Spirit of God has made me, and the breath of the Almighty gives me life. – Elihu, in Job 33:4
In the first part of this “Breath of Life” article, I discussed the importance of spirit (ruwach) as both the material and non-material animation of many living things. I also considered the idea of being spiritual (pneumatikos) as not so much about being pious as about really living—being animated as God intended. In this continuation, I want to have a look at the full journey of oxygen—that vital constituent in the breath of life—from the air to the body’s cells. And, of course, I hope to make analogous application for our lives.
Though we likely think of breathing as primarily a lung activity, this is only its beginning. One might break it down like this: Oxygen must be brought into the lungs, then into the blood, delivered to the cells, and then effectively used by those cells.
Firstly, we consider getting the oxygen into the lungs, or “pulmonary ventilation.” A typical adult male has a relaxed lung volume (“Functional Residual Capacity,” FRC) of about 2300mL. The lungs, however, can be squeezed to force out about 1100mL of additional air (“Expiratory Reserve Volume,” ERV). That leaves a minimum size (after maximum exhalation) of 1200mL, the “Residual Volume” (RV). Above the relaxed state, a normal inhaled breath has a “Tidal Volume” (TV) of 500mL. Yet, just as one can forcefully exhale, one can forcefully inhale, such as during exercise, a big sigh, or in preparation for being really loud. This forced-in volume is 3000mL above a normal breath. So, adding up everything, it goes like this: Forced inhalation (IRV, 3000mL) plus regular inhalation/exhalation (TV, 500mL) plus forced exhalation (ERV, 1100mL) equals 4600mL for full-on breathing, or about 1.2 gallons at a time, if one is really huffing it! Including the minimium size (RV, 1200mL), that’s a TLC (not “Tender Loving Care”, but “Total Lung Capacity”) of 5800mL, or about 1½ gallons.
All this, of course, is to bring oxygen into and out of the lungs, where it can flow among blood capillaries (porous vessels, like mini soaker hoses) that are masterfully weaved in the many-folded alveoli. This is known as gas exchange, because oxygen (O2) is being traded for carbon dioxide (CO2). Yet it is a common misunderstanding that we simply breathe in oxygen and breathe out carbon dioxide, and though breathing is not complicated, it is neither that mathematically simple. Seventy-eight percent of air is nitrogen gas, and about 1% is argon, both of which just go in and out. Only the 21% of air made up of oxygen has opportunity to diffuse into the blood. And of that, only about 25%, or 5.3% of the total air, actually diffuses. (This is why rescue breathing can work: If all we exhaled was carbon dioxide, rescue breathing would suffocate its intended rescuee! Yet exhaled air has still three-fourths of the original oxygen.) As for the carbon dioxide, inhaled air has almost none of it, while exhaled air has a concentration of about 4.5%. Thus, it is a gas exchange, out of total air volume, of 5.3% oxygen for 4.5% carbon dioxide. As would be expected, the amount
of oxygen making it into the blood is a function not only of breathing volume and rate, but also the health of the lungs’ alveoli; unhealthy lungs will perform below the 25% rate of diffusion.
The third step is the delivery of oxygen to cells via the bloodstream. Though we might hear of the famed lung capacity of the Nepali Sherpa, or of a great endurance athlete, it is not lung capacity alone that makes for their great abilities. Any oxygen diffused into the blood at the lungs must yet travel to the cells where it is needed. This requires “cardiac output,” which is the product of the heart’s stroke volume and the heart rate. An average healthy male can move about five liters of blood per minute while at rest, and up to sixteen liters during intense activity. A trained athlete moves slightly more blood at rest, yet close to twenty liters per minute during competition! This is especially impressive when one recognizes that there are only about five liters of blood to move at all. Thus it is aptly called “circulation”! Interestingly, the engineered method of oxygen transport is to bind each four oxygen molecules to four iron atoms in a massive macromolecule known as hemoglobin. The molecule itself is over 500 times the weight of the oxygen atoms it carries!
Clearly, the more blood that is moved, the more oxygen delivered. And yet it will only be delivered to where it is effectively used. So, fourthly, cells must develop the mechanisms to burn fuel using oxygen. When something is lit on fire—“combustion”—fuel and oxygen produce heat, carbon dioxide, and water. Yet when a cell “burns,” the process is far more complex, and is known as “aerobic cellular respiration.” Greatly simplified here: fuel (sugars) with oxygen produces heat, carbon dioxide, and water (as with combustion), yet additionally, motion, and energy for maintenance and growth.
The capacity of steps three and four together are known as the “VO2 max,” typically expressed in milliliters of oxygen per kilogram of body mass, per minute. The average male can deliver and 
use 45mL per kg per minute. For a 165-lb male, this means that about 3400mL of oxygen can be delivered to the body per minute. If a typical male breathes deeply a rapid rate of, say, thirty breaths per minute, that can supply about 5500mL of actual diffusible oxygen…well above what the body can even use! Thus, the amount of oxygen getting into the lungs is only as good as the amount that can be scurried out of there by fast-moving blood in amazing networks of vessels. Furthermore, this amount is only as good as that which can be effectively employed by the cells’ powerhouses, while still maintaining the proper cell environment. So if you’re short of breath, it’s likely that you should blame your cells first, not your lungs.
Our cells can, however, burn fuel without oxygen—“anaerobic cellular respiration”—but only for a time, and we feel the burn as this forces cells into a painful acidic state that must be reversed. It is “matter over mind” at this point, until time and oxygen get things back to normal.
So, to summarize, the full extent of breathing involves:
Pulmonary Ventilation (bringing oxygen into the body)
…product of Vital Capacity x Respiratory Rate
Gas Exchange (bringing oxygen into the blood)
…requiring healthy alveoli, red blood cells, and hemoglobin
Circulation (delivering oxygen to the cells)
…product of Heart Stroke Volume x Heart Rate
Aerobic Cellular Respiration (using oxygen in the cells)
…a complex process employing mitochondrion and acid removal
What can we make of all this? Firstly, we see the biblical wisdom of the statement “The life [nephesh, or soul] is in the blood” (Leviticus 17:11,14; Deuteronomy 12:23). Long before we had the scientific knowledge to put this together, before closed circulation was understood, and while bloodletting was still practiced as a therapy, the Scriptures stated that what animates us is in the blood.
Secondly, we can extract deeper application from the command to “be filled with the Spirit” (Ephesians 5:18), or the idea that “the Spirit searches all things, yes the deep things of God” (1 Corinthians 2:10), or that “the spirit of a man is the lamp of the Lord, searching all the inner depths of his heart” (Proverbs 20:27). The spirit, both in its material and nonmaterial sense (recall from part I of this article that these are practically inseparable), is to be penetrating and pervasive. God wants his Spirit activated in one’s entire being, just as oxygen finds its way to all of a person’s trillions of cells. God desires “truth in the inner parts” (Psalm 51:6), and what better way than to be “strengthened with might through His Spirit in the inner man” (Ephesians 3:16)?
How are we so infused by God’s Spirit? If we compare this to the full process of breathing and aerobic conditioning, we see that being filled with the Spirit is not merely about a well-intentioned occasional effort, but about consistently exercising our spiritual capacity. The more we live and breathe in Christ’s Spirit, and the more we train a spiritual heart (that is, doing works from the right motives), the greater our spiritual “VO2 max.” Perhaps the adaptive effect of increased blood vessels and mitochondrion through aerobic conditioning can be paralleled to our spiritual growth. “For bodily exercise profits a little, but godliness is profitable for all things, having promise of the life that now is and of that which is to come” (1 Timothy 4:8). A fleshly Christian seeking occasionally to do God’s work in a deeper way is like a couch potato trying to complete a distance runner’s interval workout. Ironically, though Christ’s Spirit is plentiful, we may find ourselves gasping for Him, not getting enough; we may “bonk” spiritually simply because we haven’t persevered previously. Being filled with the Spirit is a long-term training objective—a state realized certainly by God’s grace, but not without our submission to an ongoing regimen.
To be animated in the life that God desires for us—to be godly—we must breathe within. And to do so, we must do so consistently and increasingly. We cannot be “anaerobic Christians” for any meaningful stretch of time. Yet patient spiritual training makes even day-to-day “breathing” less laborious, and makes us more effective partakers and participants in His spiritual work. “Do you not know that those who run in a race all run, but one receives the prize? Run in such a way that you may obtain it. Everyone who competes in the games goes into strict training. They do it to get a crown that will not last; but we do it to get a crown that will last forever” (1 Corinthians 9:24-25).
© 2009 Chard Berndt.
All Scriptures NKJV.
Last essay of 2009 almost up…
“The Breath of Life, Part II” is just around the corner. I hope you all will be motivated to “breathe within”, both in your physical and spiritual health. Back to you tomorrow or Wednesday.